What's the meaning of the word 'Unlimited' in the volume discounts table?

The word 'Unlimited' means that you can buy any copies of the Single License as you like. And it includes the number of people in a corporate.

For example, if there are 30 staffs in your company, you can just buy 30 licenses for them, but you don't have any licenses available for the new coming staff. If you buy a Corporate License, any number of your staffs in a corporate can use the software at the same time.